I make skating dresses for a living so make all my own competition/practice apparel. I can't really offer brand suggestions but I can offer some tips on what I've found to flatter myself and other adults!
Things that I feel flatter an adults body:
Velvet is more forgiving then lycra. Whichever one you pick, make sure it has at least a front lining, better to have entire bodice lined. This helps smooth any lumps and bumps, especially in the midsection.
Skirts should be slightly longer in the back. This is true for any skater but especially for adults. If the skirt is the same length before you put it on your body, when you wear it, the back will look too short.
Avoid full circle skirts. Too much fullness for anyone with hips, plus they aren't in style right now. Semi circle can be very flattering if it falls at the right point on your body.
Boycut briefs are not flattering.
If you need a bra, make sure you can wear one under the dress without seeing it or have your dressmaker build one into the dress. I frequently line any mesh areas of my dresses with a matching nude lycra.
Hope that helps someone!